As portable electronic devices, there are mobile phones, tablet terminals, digital cameras, notebook PCs, PDAs (Personal Digital Assistants), portable DVD (Digital Versatile Disk) players, portable music players, and portable televisions, for example.
The mobile phone, one kind of portable electronic devices, has a configuration as shown in FIG. 5, for example. That is, a mobile phone 100 shown in FIG. 5 includes a speaker (not shown) in the front of a case 200, various sensors (e.g., an acceleration sensor and a gyroscopic sensor) 300 near the speaker, and a light source 400 such as an LED (Light Emitting Diode), and the like.
These devices such as the speaker, the sensor 300, and the light source 400 are covered with a covering member 500 from above the case 200. The case and the covering member 500 have an opening 510 for propagating sound from the speaker to the outside. The covering member 500 is made of a relatively flexible member from viewpoints such as to ensure the performance of the speaker and the sensor 300 and to ensure transmittance of light emitted from the light source 400. Therefore, measures are taken not to damage the covering member 500 in case the mobile phone 100 is dropped, such that a periphery of the case 200 is covered with a soft case 600.
Incidentally, patent literatures 1 to 3 disclose techniques of forming a protrusion on a case of a portable electronic device. In patent literature 1, the protrusion is formed on the case to propagate sound to the outside when the portable electronic device is placed on a desk, for example, with an opening side of the case facing downward. In patent literature 2, the protrusion is formed on the case so as to reduce contact of an ear with the case when a user brings the user's ear close to an opening of the case in order to receive a call. In patent literature 3, the protrusion made of a soft elastomer is formed on edges of the case so as not to damage the portable electric device in the event of a fall.